Current therapies for autoimmunity are frequently unable to induce durable remissions and are limited by significant toxicities. Antigen-specific immunotherapies may be less toxic and more potent. Formulating a scientific basis for their use is therefore critical. We have developed a novel antigen-specific immunotherapy for the treatment of autoimmunity. By transgenically expressing on T-cells chimeric receptors that link autoantigen-MHC and signaling regions from the TCR we are able to specifically redirect therapeutic T-cells against autoreactive T-cells. Engagement of the chimeric receptor by the autoreactive T-cell's TCR stimulates endogenous immunoregulatory functions of the therapeutic cell. In preliminary studies we have shown that T cells expressing these chimeric receptors (receptor-modified T-cells, RMTC) are highly effective in treating a model autoimmune disease, experimental allergic encephalomyelitis (EAE). Our results have led to several hypotheses. Hypothesis 1: RMTC may be applied to treat human autoimmune disease. Our preliminary results showed that treatment of autoimmunity with RMTC directed against T cells specific for one autoantigenic epitope can globally down modulate the autoimmune response. We will create humanized RMTC specific for autoreactive T cells found in patients with multiple sclerosis and test whether similar potency can be achieved in pre-clinical models. Hypothesis 2: RMTC form a family of therapeutic cells that tolerize autoreactive T-cells through different mechanisms. Our preliminary results showed that CD8 +, CD4+CD25 +,and Th2 RMTC, but not other RMTC types are effective in alleviating EAE. We will therefore study the mechanism of action of these RMTC subsets. We will further analyze whether, by targeting autoreactive T cells, RMTC can suppress autoantibody production and pathology in collagen-induced arthritis. Hypothesis 3: RMTC modify the migration and cellular dynamics of autoreactive T cells. We will quantitatively analyze the migration and longevity of RMTC and their autoreactive target cells. Parallel studies will assess the colocalization of RMTC with their targets in vivo. Hypothesis 4: The functional capabilities of RMTC depend upon chimeric receptor avidity for cognate TCR and signaling domain potency. We will determine how a target cell's antigen avidity, the RMTC's chimeric receptor expression level, and the chimeric receptor signaling domain's potency influence RMTC response. These studies will enhance our understanding of how active autoimmune responses can be downmodulated by antigen-specific immunotherapies and provide a scientific basis for the application of RMTC and other cellular therapeutic approaches. [unreadable] [unreadable]